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Scientists have edited human embryos for the first time in the UK to discover a “master gene” that underpins successful pregnancies. The “game-changing” research promises improved IVF outcomes and a breakthrough in understanding why so many pregnancies fail.

The Government-funded investigation, undertaken by the Francis Crick Institute, is the first to prove that gene editing can be used to study the genetic behaviour of human embryos in their first few days of life.

If we knew the key genes that embryos need to develop successfully, we could improve IVF treatments and understand some causes of pregnancy failureDr Kathy Niakan, Francis Crick Institute

By removing a gene which produces a protein called OCT4, the team discovered it was crucial to a viable pregnancy.

As well as its potential for more successful IVF, the discovery heralds a transformation in understanding the fundamental causes of infertility and miscarriage.

Approximately one in four couples are affected by fertility problems, and women under 35 currently have just a 32.2 per cent chance of a live birth from one round of IVF.

The odds decrease to 27.7 for women aged 35 to 37, and to 20.8 per cent for those aged 38 and 39.

Licenced by the Human Fertilisation and Embryology Authority, the research is controversial because it uses a similar technique to that employed increating so-called “designer babies”, where genetic defaults are edited out at an embryonic stage.

However, the Francis Crick team say their work is intended purely to understand the early stages of conception.

Under the terms of their licence, the modified human embryos must be destroyed after 14 days.

The research was undertaken at the Francis Crick InstituteCredit:
Daniel Leal-Olivas

Dr Kathy Niakan, who led the research, said: “One way to find out what a gene does in the developing embryo is to see what happens when it isn’t working.

“Now we have demonstrated an efficient way of doing this, we hope that other scientists will use it to find out the roles of other genes.

“If we knew the key genes that embryos need to develop successfully, we could improve IVF treatments and understand some causes of pregnancy failure.”

The scientists, who studied 41 human embryos donated by IVF patients, used the gene-editing tool Crispr/Cas9 to make precise cuts in DNA and deactivate OCT4.

They found OCT4 appeared to be necessary for an embryo to become a blastocyst, a tiny ball of 200 cells that arises a week after conception and marks a key point in embryonic development.

Only when an embryo successfully reaches the blastocyst stage does it stand any chance of implanting in the womb.

The study, published in the journal Nature, found fewer than a fifth of the test embryos reached the blastocyst stage without OCT4.